Miniature triode oscillator for high frequency operation



Dec. Z2, 1964 c. A. BEATY I 3,152,823

MINIATURE TRIODE OSCILLATOR FOR HIGH FREQUENCY OPERATION Filed Aug. 29, 1961 3 Sheets-Sheet l 6K l D f5 EMI/VA L f//cfw FREQUENC v g asc /4 L A rok /4 [/4 mmf W HNO DE TEIMM/d L T' 1U @y f/ a FERRI TE l VIIIIIIZ.

Dec. 22, 1964 c. A. BEATY 3,162,823

MINIATURE TRIoDE oscILLAToR FOR HIGH FREQUENCY OPERATION Filed Aug. 29, 1961 s sheets-sheet 2 Dec. 22, 1964 c. A. BEATY 3,162,823

MINIATURE TRIODE OSCILLATOR FOR HIGH FREQUENCY OPERATION Filed Aug. 29, 1961 6R70 TEeMl/VAL,

3 Sheets-Sheet 5 34 di! d" ,Q ,r au rpuf /A/aEPENoE/vv-y Mov/751.5 Edili/A165 HEATER P/A/ JOCKETJ United States atent iifice 3,152,823 Patented Dec. 22, 1964 3,162,823 MINIATURE TRIGDE GSCILLATGR EGR HIGH FREQUENCY GPERATIGN Charles A. Beaty, Tampa, Eta., assigner to Trai( Microwave Corporation, Tampa, Fla. Filed Ang. 29, 1961, Ser. No. 134,724 7 Claims. (Cl. 331-97) This invention relates to the generation of high frequency electrical signals and in particular to ultra high frequency and microwave oscillators.

The invention is described as embodied in a tunedplate, tuned-cathode, and grounded-grid oscillator in which strip line techniques are made use of to form equivalent tuned coaxial lines.

' It is among the objects of this invention to provide an oscillator of miniature size.

Another object of ythe invention is to provide an oscillator having two separate distributed tuned circuits in juxtaposition.

Still another object of the invention resides in the con-,

struction of resonant coaxial lines positioned side-by-side Within au integral metal housing.

It is still another object of the invention to provide measn for making D.C. connections to the vacuum tube elements through the interior of a coaxial line center conductor.

Another object of the invention is to provide a coaxial line center conductor in the form of a cantilever beam having on the free end thereof means for making contact with an active tube element, and means acting through the cantilever beam for maintaining continuous pressure between the free end of the beam and the terminal of the tube.

Another object of the invention is to provide improved means for preventing the leakage of R.F. energy from the oscillator.

Still another object is to provide improved means for manually varying the frequency of operation.

Still another object is to provide a compact oscillator which can be readily assembled and disassembled.

These and other objects will be in part pointed out in and part apparent from the following description considered in conjunction with the accompanying drawings, in which:

- FIGURE l is a plan View of an oscillator embodying the invention;

FIGURE 2 is a longitudinal section taken along line 2 2 of FIGURE l showing the two juxtaposed coaxial line cavities;

FIGURE 3 is a plan View of the inner conductor of the anode line with the right-hand portion of the structure shown in horizontal axial section to expose the lter assembly;

FIGURE 4 is a view in side elevation of the anode line shown in FIGURE 3 with a portion of the structure sectioned to show the construction of the anode socket;

FIGURE 5 is a bottom plan view of the inner conductor of the cathode line with a portion oi the structure sectioned to show the arrangement of the cathode filter;

FIGURE 6 is a view in side elevation of the inner conductor shown in FIGURE 5;

FIGURE 7 is a perspective view of a vcuum tube suitable for use in the oscillator;

FIGURE 8 is a top plan View similar to FIGURE l but with the cover and anode conductor structure removed, showing the mounting of the tube` in the oscillator housing, and with a portion of the outer shell being cut away to show the connecting means for the grid circuit; FIGURE 9 is a vertical sectional view of the oscillator shell taken along line @-9 of FIGURE 8;

FIGURE 9A is a sectional detailed view also taken on line 9 9 of FIGURE 8; and

FIGURE l0 is a partial sectional view taken along line lil-1i) of FIGURE 5 showing the construction of the cathode socket.

In the description and claims related to the invention, the term coaxial line is not limited to one in which the inner and outer conductors are circular in cross-section nor is the term limited to one in which the two conductors have the same cross-sectional shape. The term is intended rather to refer to lines which operate electrically in the manner of coaxial lines with concentric elements and in which a central conductor is positioned within a conductive surface completely surrounding and spaced from the central conductor.

The oscillator shown in FIGURE 1 is housed in a shell forming an outer conductor and generally indicated at 4 formed of silverplated brass, aluminum or othervsuitable material. The outer conductor shell 4 may beformed, for example, from `a square metal bar by bobbing out portions of the metal on the upper and lower sides to form two cavities, generally indicated at 6 and 8 in FIG- URE 2, separated by a transverse partition It). One side of the cavity 6 is closed by means of a cover plate I2 secured by screws 14. One side of the other cavity 8 is closed in similar manner by a cover plate 16.

In this particular example the oscillator makes use of a ceramic type triode vacuum tube having planar grid, cathode, and'anode elements. Such a tube is sold by Trak Microwave Corporation, Tampa, Florida, under number TK-9127 and by General Electric Company under the designation 7486. This tube, generally indicated at 17 in FIGURE 7, is provided with two heater pins 18A and 18B extending from the end of the ceramic body. Contact to the cathode is made through a cathode-contact ring 2d recessed below the surface of the tube. Contact to the gride is made through a grid-contact ring 22 formed integrally with the tube and extending outwardly from the ceramic body. Connection to the anode is made through an anode cap 24 positioned on the opposite end of the tube from the heater contact pins 18A and 18B.

The tube I7 extends through a threaded opening 26 (FIGURE 8) in the partition 10 with the anode cap 24V projecting into the anode coaxial line cavity 6 and the cathode 20 and heater pins ISA and 18B extending into the cathode coaxial line cavity 3.

The grid contact ring 22 is positioned in the opening 26 in the partition I@ where it is anchored by two annular nuts 2g and 219. The grid-contact ring 22 is positioned againstv and makes contact with a metal washer 39 positioned within the hole 26 and is insulated from the nut 29 by a dielectric washer 32. The grid washer 30 is separated from the nut 28 by a dielectric washer 33. The grid washer 30 is connected by means of an insulated lead 34 (FIGURES 8 and 8A) extending through the partition l@ and through the outer wall of the housing 4 to an external terminal 36. Thus, the grid of the tube I7 is maintained at the same R.F. potential as the shell 4 by the capacity through the dielectric washers 32 and 33 but is insulated from the shell so far as direct current is concerned. In this example there is a capacity of about 50 paf. between the grid ring 22 and the shell 4. Inopertion, the terminal 36 may be connected to the shell. 4

through a fixed resistor mounted on the outside of the structure.

In order to make contact with the cathode-contact ring 20, two 'semi-annular cathode-contact bushings 38A and 38B (FIGURE 9A) are positioned around the contact ring Ztl with their inner-surfaces dimensioned tot make intimate contact throughout the circumference of the cathode-con'- tact ring 26. The louter surface of a cathode socket 40 3 (FIGURE l) is formed of beryllium copper or othe suitable material and has annularly arranged spring 1ingers 42 to insure low inductance contact completely around the cathode-contact bushings 38A and 38B. The free end of each of the fingers 42 is tapered as shown at 44 so that the socket will slide over the cathode-contact bushings 38A and 318B.

The annular cathode socket 4.6 is secured by Soldering or other means to a cathode line inner conductor 46 (FIG- URE 6) which extends longitudinally within the Cathode cavity 8 (FIGURE 2) and which is secured to and supported-by a terminal block 48 which fits within the en portion of the shell 4 (FIGURE 2).. t

Contact is made to the heater contact. pins 18A and 18BI by means of two heater pin sockets 49 which are provided with a cup-shaped portion 50 (FIGURE l0) formed of peripherally arranged spring lingers and a base portion 52. which extends through a clearance opening in a plastic sheet 54 covering the base end of the cathode socket 4i). The plastic sheet member 54 is Secured by a single screw 56 to the cathode line inner conductor 46. The base portion 52 of each socket 49 fits loosely in the plastic sheet 54. soI that each of the sockets 49 can move independently, laterally and angularly enough to accommodate variations in the positions and angles of the heater pins 18A and 18B. Since the plastic sheet 54 is secured only by the. screw 5.6, it serves asV a spring member lfree to. ex suiciently to accommodate differences in longitudinal dimensions of the. tube 17, that is, variations in the distanceV between the grid-contact ring' 22 and the endsV of .the heater Pins 118A andV 18B, @ne of the heater pin sockets 4-9 isconnected by ,a metal strap 5.8 (FlGUREV 5) to the screw 56. and through the cathode line inner conductor line 46 andv metal terminal block 48 to the shell 4.

In: order to. provide al connectionl for the other heater sokft 4.9, its base portion 5,2- is connected to an insulatedV lead' 59. which passes through a groove 60 in one side Qt thecathode line inner conductor 46 and through an Opening 62,: inthe suppertng bleek 43. In Order to PreventY leakage of. R-F energy, a low-pase. tlter generally indicatedat; 6.4-, is bultwithdthe terminal block 4.8. Thel lead; 59: passes directly. through. the block and :is secured to a solder terminal; 6.26. Qu the outer'end.: 0f the block 48- This portion of the wire within the block 48 is surrounded by a cylindrical length df ferrite 6.8, which may, for examplq to be a conventional ferrite formed of zinc, manganese and' iron oxides. At; the. point where the Wire 5.9,-entere. the ferrite 6.8., it is soldered t0 a metal Cup 72 which surrounds one end of the ferrite and extends along itsperiphery for a distance slightly lessthan one-half the lengthv of the ferrite 68. A. similar metal cup 74 isv formedI integrally with the solder terminal 6,6 and fits over the Opposite end-.of the ferrite but deesY not make electrical; contact with the cup` 72. The twoecupsV 72 and 74 are insulated from the metal block 48 by a layer '76` offdielectr-.C material; such as Mylar lm. With this arf rangementfthe. cups 72; and 74 serve respectively asl input and output capacitors'` separated by thel inductance added 'to thecircuit. by the ferrite cylinder 68. The wire 59 In operation it is desirable that the cathode circuit beA tuned to yajsliglltly lower frequency than the anode circuit. This can be ed:@.rrntlielietA by lengthening the cathode inner.A conductor 46- However, the Same eiect een be achieved withia correspondingly shorterover-all oscillator lengthby formingapcentral opening Aas indicated at 7 8 in FIGURE. 5,. The resultinadiyisvn .O ftbe line; 46. into two separated parallel branches for a portion of its length increases the characteristic impedance and lowers the resonant frequency of the line.

To provide sustained oscillation, it is necessary to feed back R-F energy from the anode line cavity 6 to the cathode line cavity 3. This is accomplished by means of an adjusting screw (FIGURES 2 and 6) which is in threaded engagement with a spl-it bushnig 82 mounted in the cathode line inner conductor 46 and has a capacity probe 84 secured to one end, The screw 80 extends through a clearance opening S3 (FIGURE v8) in the partition lll into the anode line cavity 6. Y Y

Connection is made to the anode cap 24 by means of an anode socket 86 (FIGURE 4) formed of beryllium copper, Phosphor bronze, or other suitable spring contact material and having spring lingers 88 adapted to make circumferential contact with the anode cap 24. A threaded shank Sti is secured to the head portion of the socket 86 and extends through the anode linev inner couductor 9:2 into threaded engagement with a nut 94. The head portion of the socket 86 is insulated' from the conductor 92 by a dielectric washer 95, and the shank Y9E? is insulated from the line 92 by an insulated bushnig 96. A solder terminal 98 is positioned beneath the nut 94 and vinsulated from .the lineV 92 by a dielectricV Washer 100. The dielectric washers and lut) andV the bushing 96 provide Vsutiicient capacity coupling between the anode cap and the conductor 92 to provide a low-impedance path for R-F current.' Y

In order to proyide B+ voltage for theV anode, aninsulated wire lead 102 (FIGURE 3) is connected to the terminal $3 and extends Within a groove l04 in the `surface of the anode line innerconductor 92 and this groove extends to a metal terminal block 166 which is connected to the end of and supports the anode line 92.

The lead 1.02 passes throughY a lowpass lter assembly, generally indicated at 64A, to an external 4solder terminalv 66A. This filter 66A may be identical with the filter 64 described in connection with the' cathode line inner conductor 46 and corresponding parts have been correspondingly numbered followed by the suilix A.

In order to maintainV firm Contact between the anode socket S6 and the anode cap 24, the terminal block 106 is formed. so that its dimensioniindicatedV at l10.8- in FIG- URE 2 is preferably slightly greater, for example, by one thousandth of an inch or less, than the'height of the adjacent sidewalls of the shell 4.so that when the plate 12 is tightened into position` by means ofthe' screws 14, the cantilever-supported socket 86 is maintained under con-Y tinuous pressure against the anode cap 24.

Thus, the oscillator includes two juxtaposedvone-quarter wavelength parallel Acoaxial lines resulting in significant saving, of length over arrangementsin which the coaxialY lines are arranged in end-to-end or only partially overlapping relationship. f

The anode line is the primary frequency determining element, and its operating frequency is adjusted by means of a screw (FIGURE 2) which is in threaded en- Y gagement with the plate 12 andextends into the 'anode line cavity directly opposite the anode cap 24 of the tube. After adjustment tothe desired frequency, theV screw 110 is locked in position by means of a nut 112.

' By means of this arrangement a tuning range of 5 to l0 vides significant advantages in size and operational characteristics over those heretofore obtainable andwhich is suited for use under a variety of conditions and in particular for rigorous commercial and military applications.

What is claimed is:

1. A high frequency oscillator comprising a tube having a cathode, a grid, and an anode, a first coaxial line having an inner and an outer conductor, means coupling the inner conductor of said first coaxial line to said cathode, the inner conductor of said first coaxial line having a portion of reduced cross section formed by two spaced parallel arms, a second coaxial line having an inner and an outer conductor, means coupling said inner conductor of said second coaxial line to said anode, said first and second coaxial lines being substantially parallel and positioned in side-by-side relationship, and having a length of approximately one quarter Wave length, and housing means surrounding both of said coaxial lines and forming said outer conductors of both coaxial lines.

2. A high frequency oscillator comprising a tube having a cathode, a grid, and an anode, a first coaxial line having an inner and an outer conductor, means coupling the inner conductor of said first coaxial line to said cathode, a second coaxial line having an inner and an outer conductor, means coupling said inner conductor of said second coaxial line to said anode, said first and second coaxial lines being substantially parallel and positioned in side-by-side relationship, and first and second D.C. connecting means respectively extending along and recessed within and being insulated from said inner conductors of said first and second coaxial lines.

3. A high frequency oscillator comprising an electron tube having a cathode, a grid, and an anode, a shell housing of conductive material having first and second internal cavities, means for supporting said tube within said shell housing with portions of said tube extending into each of said cavities, a first quarter-wave anode inner conductor coupled to said anode and extending within said rst cavity, a second quarter-wave cathode inner conductor coupled to said cathode and extending within said second cavity, means for making D.C. connection to said anode including a D.C. conductor extending longitudinally along, recessed within, and insulated from said anode inner conductor, said D.C. conductor extending outwardly through said housing, and a low-pass filter for said D.C. connection including a member of ferrite material surrounding asid D.-C. conductor and positioned within said shell housing.

4. A high frequency oscillator comprising a tube having a cathode, a grid, an anode, and first and second heater contact pins, a shell of conductive material having first and second internal cavities, means supporting said tube within said shell with portions of said tube extending into each of said cavities, capacitive means forming a low-impedance R-F path between said grid and said shell, an anode inner conductor coupled to said anode and extending Within said first cavity, a cathode inner conductor coupled to said cathode and extending within said second cavity, rst and second heater pin sockets adapted to engage and make contact with said heater contact pins, and spring means secured to said cathode inner conductor and resiliently supporting said sockets for engagement with said heater pins.

5. A high frequency oscillator comprising a tube having a cathode, a grid, and an anode, a shell of conductive material having first and second internal cavities, said cavities extending in parallel side-by-side relationship, means supporting said tube within said shell with portions of said tube extending into each of said cavities, capacitive means forming a low-impedance R-F path between said grid and said shell, a rst quarter-wave anode inner conductor coupled to said anode and extending within said first cavity, a second quarter-wave cathode inner conductor having a portion of reduced cross section and coupled to said cathode and extending within said second cavity, rst D.C. connecting means extending from said anode along and beneath the surface of said first inner conductor and extending outwardly through said shell, second D.C. connection means extending from said cathode along and beneath the surface of said second inner conductor and extending outwardly through said shell, and first and seco-nd low-pass filter means connected respectively with said first and second connecting means and positioned within the conductive material of said shell.

6. In an oscillator having an outer conductive shell, and a vacuum tube having anode and cathode electrodes, a tuned circuit coupled to each said electrode and positioned within said shell, means for making D.-C. connection to each said electrode including a low-pass filter and a conductor connected to each said electrode, said lter having a sheath of ferrite metal surrounding said conductor, and a metal cup partially surrounding said ferrite sheath and connected to said conductor, said metal cup being positioned in said shell and a thin layer of insulation material for insulating said cup from said shell providing capacitance between said cup and shell.

7. A high frequency oscillator comprising an elongated generally rectangular metal shell having a transverse metal partition therein forming first and second internal juxtaposed cavities on opposite sides of said partition, a vacuum tube having first and second heater contact pins, a cathode-contact ring, a grid-contact ring, and an anode cap, said tube extending through said partition and having said anode cap positioned in said first cavity and said cathode-contact ring and heater contact pins positioned in said second cavity, capacitance means coupling said grid-contact ring to said partition, an anode line inner conductor extending longitudinally within said first cavity, socket means at one end of said anode line arranged to engage said anode cap, means at the opposite end of said anode line forming part of said housing and arranged to support said anode line inner conductor, a cathode line inner conductor extending longitudinally within said second cavity, means -at one end of said cathode line coupling it to said cathode-contact ring, means at the `opposite end of said cathode line forming part of said housing and supporting said cathode line inner conductor, heater pin socket means for engaging said heater pins, resilient support means for said heater pin socket means mounted on said cathode line inner conductor, and conductive means extending lengthwise within the surface of said cathode line inner conductor for making connection to said heater pin socket means.

References Cited by the Examiner UNITED STATES PATENTS 2,451,502 10/48 Lisman et al. 331-98 2,531,693 11/50 Lansmau 331-98 2,762,918 9/56 Wise 331-98 2,763,783 9/56 Lorenzen 331-98 ROY LAKE, Primary Examiner.

JOHN KOMINSKI, Examiner, 

1. A HIGH FREQUENCY OSCILLATOR COMPRISING A TUBE HAVING A CATHODE, A GRID, AND AN ANODE, A FIRST COAXIAL LINE HAVING AN INNER AND AN OUTER CONDUCTOR, MEANS COUPLING THE INNER CONDUCTOR OF SAID FIRST COAXIAL LINE TO SAID CATHODE, THE INNER CONDUCTOR OF SAID FIRST COAXIAL LINE HAVING A PORTION OF REDUCED CROSS SECTION FORMED BY TWO SPACED PARALLEL ARMS, A SECOND COAXIAL LINE HAVING AN INNER AND AN OUTER CONDUCTOR, MEANS COUPLING SAID INNER CONDUCTOR OF SAID SECOND COAXIAL LINE TO SAID ANODE, SAID FIRST AND SECOND COAXIAL LINES BEING SUBSTANTIALLY PARALLEL AND POSITIONED IN SIDE-BY-SIDE RELATIONSHIP, AND HAVING A LENGTH OF APPROXIMATELY ONE QUARTER WAVE LENGTH, AND HOUSING MEANS SURROUNDING BOTH OF SAID COAXIAL LINES AND FORMING SAID OUTER CONDUCTORS OF BOTH COAXIAL LINES. 